Double-sided tapes and tape changers

1 files changed, 183 insertions, 0 deletions

diff --git a/BJC-Utils2/src/main/java/bjc/utils/esodata/SingleTape.java b/BJC-Utils2/src/main/java/bjc/utils/esodata/SingleTape.java
new file mode 100644
index 0000000..0e0deb2
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/esodata/SingleTape.java
@@ -0,0 +1,183 @@
+package bjc.utils.esodata;
+
+import java.util.ArrayList;
+
+/**
+ * A tape is a one-dimensional array that can only be accessed in one position at a time.
+ *
+ * A tape is essentially a 1D array with a cursor attached to it, and you can only
+ * affect elements at that cursor. The size of the array is theoretically unbounded
+ * to the right, but in practice bounded by available memory.
+ *
+ * You can choose whether or not you want the tape to automatically extend itself to the
+ * right with null elements by specifiying its auto-extension policy.
+ *
+ * @param T The element type of the tape.
+ * @author bjculkin
+ */
+public class SingleTape<T> implements Tape<T> {
+	protected ArrayList<T> backing;
+	protected int pos;
+
+	protected boolean autoExtend;
+
+	/**
+	 * Create a new empty tape that doesn't autoextend.
+	 */
+	public SingleTape() {
+		this(false);
+	}
+
+	/**
+	 * Create a new empty tape that follows the specified auto-extension policy.
+	 *
+	 * @param autoExtnd Whether or not to auto-extend the tape to the right
+	 * 			w/ nulls.
+	 */
+	public SingleTape(boolean autoExtnd) {
+		autoExtend = autoExtnd;
+
+		backing = new ArrayList<>();
+	}
+
+	/**
+	 * Get the item the tape is currently on.
+	 *
+	 * @return The item the tape is on.
+	 */
+	public T item() {
+		return backing.get(pos);
+	}
+
+	/**
+	 * Set the item the tape is currently on.
+	 *
+	 * @param itm The new value for the tape item.
+	 */
+	public void item(T itm) {
+		backing.set(pos, itm);
+	}
+
+	/**
+	 * Get the current number of elements in the tape.
+	 *
+	 * @return The current number of elements in the tape.
+	 */
+	public int size() {
+		return backing.size();
+	}
+
+	/**
+	 * Insert an element before the current item.
+	 *
+	 * @param itm The item to add.
+	 */
+	public void insertBefore(T itm) {
+		backing.add(pos, itm);
+	}
+
+	/**
+	 * Insert an element after the current item.
+	 */
+	public void insertAfter(T itm) {
+		if(pos == (backing.size() - 1)) backing.add(itm);
+		else							backing.add(pos+1, itm);
+	}
+
+	/**
+	 * Remove the current element.
+	 * 
+	 * Also moves the cursor back one step if possible to maintain
+	 * relative position.
+	 *
+	 * @return The removed item.
+	 */
+	public T remove() {
+		T res = backing.remove(pos);
+		if(pos != 0) pos -= 1;
+		return res;
+	}
+
+	/**
+	 * Move the cursor to the left-most position.
+	 */
+	public void first() {
+		pos = 0;
+	}
+
+	/**
+	 * Move the cursor the right-most position.
+	 */
+	public void last() {
+		pos = backing.size() - 1;
+	}
+
+	/**
+	 * Move the cursor one space left.
+	 *
+	 * The cursor can't go past zero.
+	 *
+	 * @return True if the cursor was moved left.
+	 */
+	public boolean left() {
+		return left(1);
+	}
+
+	/**
+	 * Move the cursor the specified amount left.
+	 *
+	 * The cursor can't go past zero.
+	 * Attempts to move the cursor by amounts that would exceed zero
+	 * don't move the cursor at all.
+	 *
+	 * @param amt The amount to attempt to move the cursor left.
+	 *
+	 * @return True if the cursor was moved left.
+	 */
+	public boolean left(int amt) {
+		if((pos - amt) < 0) return false;
+
+		pos -= amt;
+		return true;
+	}
+
+	/**
+	 * Move the cursor one space right.
+	 *
+	 * Moving the cursor right will auto-extend the tape if that is enabled.
+	 *
+	 * @return Whether the cursor was moved right.
+	 */
+	public boolean right() {
+		return right(1);
+	}
+
+	/**
+	 * Move the cursor the specified amount right.
+	 *
+	 * Moving the cursor right will auto-extend the tape if that is enabled.
+	 *
+	 * @param amt The amount to move the cursor right by.
+	 *
+	 * @return Whether the cursor was moved right.
+	 */
+	public boolean right(int amt) {
+		if((pos + amt) >= (backing.size() - 1)) {
+			if(autoExtend) {
+				while((pos + amt) >= (backing.size() - 1)) {
+					backing.add(null);
+				}
+			} else {
+				return false;
+			}
+		}
+
+		pos += amt;
+		return true;
+	}
+
+	@Override
+	public boolean isDoubleSided() {
+		return false;
+	}
+}